A Crucial Theorem

His theorem is now a fundamental part of the theory of electrical engineering and was crucial in developing transmission network theory. It was to prove of immense practical value to engineers. It is now usually taught alongside its complementary theorem, Norton's Theorem, which dates from 1926 - the year Thevenin died. However, both theorems, are said to have been anticipated by the German physicist Helmholtz in l853.

Thevenin remained a bachelor for life, but provided a home for his mother's widowed cousin and her two children. Later he adopted the children.

His favourite recreation was angling and he owned a boat which he used on the River Marne for fishing. His students at the Institut Agronomique nicknamed him The Admiral. He was also a talented violinist but played only in private.

Late in 1926, Thevenin was taken to Paris for medical treatment and it was there that he died on September 21. A kindly man of simple tastes, Thevenin had requested that only his family should attend the cemetery and that a single rose from his garden should decorate his coffin. So it was when he was buried in his home town of Meaux.

Task I

Speak on Thevenin’s theorem and its impact on electrical sciences.

Task II

Retell about Thevenin’s life describing his human qualities.

Lee de forest: last of the great inventors

(1873-1961)

Although for a long time he did not have a full understanding of how it worked, Lee de Forest invented the triode, or audion as he called it. For nearly half a century it, and its descendants, dominated electronics. De Forest was also one of the earliest inventors of electronic circuits. Justifiably he could claim, therefore, to be one of the founders of electronics. Over 300 patents were filed in his name and many have regarded him as the last of the great individual inventors: but his own hope of a Nobel Prize was never fulfilled.

The name de Forest was of Huguenot origin. Lee's father, Henry Swift de Forest, was a Congregational minister¹ and principal of a school for Negroes in Talladega, Alabama. It was there that Lee grew up, having been born in Iowa at Council Bluffs on August 26, 1873. His mother, Anna Margaret Robbins, was the daughter of a Congregational minister.

A wealthy ancestor's endowment of a scholarship² at Yale University enabled de Forest to study for a bachelor's degree in mechanical engineering and he was awarded this in 1896. He followed it with a Ph.D. in 1899 for a study of the reflection of electromagnetic (Hertzian) waves from the ends of parallel wires, possibly the first Ph.D. thesis in America on a topic closely related to radio telegraphy.

By the age of 16, de Forest had announced his intention of becoming an inventor. This ambition had not dimmed by the time he left university and he determined to win fame and fortune as an inventor, with Nikola Tesla as his idol. He has also been quoted as saying that Marconi and Edison were his inspiration.

On leaving Yale, de Forest joined Western Electric in Chicago at $8 a week. But because he was never enthusiastic about working for others it was not long before his interest in radiotelegraphy led him to seek to challenge Marconi, who by then was famous. De Forest wanted his own radio system, independent of Marconi's patents, and his own company. In fact he was to found several companies over the years but he lacked the business skills which would have enabled any to survive.

At Western Electric his tinkering with radio brought no official acclaim. One day, according to his diary, he was told, "Look here, de Forest. You'll never make a telephone engineer. As far as I'm concerned ³ you can go to hell, in your own way. Do as you damn please." He took the words literally and worked full time on his own system for the remainder of his fairly short time with the company.